Field of the Invention
The invention relates to a device for holding a web of material in a rotary printing press, more particularly, having rollers over which the web is guidable, the holding device including at least one pressing element for varying web tension, and being disposed in a superstructure of the rotary printing press, especially an angle-bar or turnerbar superstructure.
The published German Patent Document G 91 09 313.9 U1 is concerned with a device for guiding a moving web. With the aid of guide elements provided with a blower or blast slot and extending over the width of the web and in the web travel direction, air is blown substantially parallel to the web travel direction. It is intended thereby to span great distances between two guide elements, for example, if a paper web which is yet moist is to be guided in a paper processing machine between a press section and a dryer section.
The published German Patent Document DE 44 08 713 A1 is concerned with a method and a device for guiding a web of material. In the embodiment described therein, which involves guiding the web in a paper-processing machine, a strip of the paper web is brought behind the press section of the paper-processing machine. Thereat, an air stream directed approximately tangentially to the guide roller from a blast nozzle device assures the transport of the paper web to a downstream unit.
The published German Patent Document DE 28 08 840 A1 discloses a pneumatically actuatable pressing roller introducible for avoiding or reducing slip between the paper web and driven rollers, particularly, in web-fed rotary printing presses. The intent is to achieve especially sensitive variation or adaptation of the necessary contact-pressure force, so that the web tension can be varied through the slip. The pressing roller should, moreover, have a low structural height. This is attained primarily by disposing a diaphragm in a first, shallow housing supported on the printing-press frame; in accordance with an adjustable air pressure in the housing, the diaphragm acts via a diaphragm plate on the bearings of the pressing roller and, accordingly, on the pressing roller itself. Pressing rollers of this type are used at the web infeed or at the driven rollers of the cooling section.
In material-processing rotary printing presses, meter-high angle-bar or turnerbar superstructures are often used, in order to collate the products, in the various configurations thereof, which can be produced with a rotary printing press, and then fold them longitudinally and/or transversely, depending upon the type of product. If an extremely undesirable break or tear in a web of material should occur in these superstructures, as a rule, the portion of the web yet remaining in the printing press ahead of or upstream from the break or tear can still be processed and can remain in the angle-bar superstructure in the prescribed web path, without requiring the web to be threaded in again thereat. Threading the web of material in again is extremely time-consuming, because the web to be threaded in again must be re-introduced into the original web path thereof by two persons, angle or turner bar by angle or turner bar, or guide roller by guide roller, in accordance with the prescribed product configuration. This takes time, requires a stoppage of production, and is therefore very expensive.